The disclosures of Japanese Patent Application Nos. HEI 11-320667 filed on Nov. 11, 1999, HEI 11-329272 filed on Nov. 19, 1999, 2000-015957 filed on Jan. 25, 2000 and 2000-014465 filed on Jan. 24, 2000, including the specifications, drawings and abstracts are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a fuel tank system and, more particularly, to a fuel tank system which is installed in a vehicle such as an automobile.
2. Description of the Related Art
Among fuel tank systems installed in a vehicle such as an automobile according to the related art, there is one employing a construction for reducing fuel vapor gas (vapor) generated from the interior of a fuel tank. Japanese Utility Model Publication No. SHO 57-168760 discloses one such example.
As shown in FIG. 8, in this fuel tank system, a conduit for communication between a fuel tank 210 and a canister 212 is provided with a check valve 216 for suitably maintaining a pressure in the fuel tank 210. In addition, a cooling device 220 is assembled with a conduit 214 between an air chamber 218 of the fuel tank 210 and the check valve 216. Thereby part of the vapor discharged from the fuel tank 210 through the conduit 214 is condensed by the cooling device 220 and returned to the fuel tank 210. Thus, the amount of vapor introduced into the canister 212 can be reduced.
However, in a fuel tank system having such a construction, since the opening pressure for the check valve 216 is set regardless of operation of the cooling device 220, it is difficult to efficiently condense vapor in accordance with the cooling capacity of the cooling device 220.
Also, it is necessary to set a large capacity for the canister 212 in consideration of the case where a large amount of vapor has flown into the canister 212 with the check valve 216 open.
It is an object of the present invention to obtain a fuel tank system capable of reducing an amount of vapor fuel to be adsorbed in a canister and making the canister compact.
According to a first aspect of the present invention, there is provided a fuel tank system comprising a fuel tank which accommodates fuel, a canister which communicates with the fuel tank through an evaporation passage, a valve member which is provided in the evaporation passage and which is opened when the system assumes a predetermined state, and cooling means which is provided in the fuel tank or in the evaporation passage from the fuel tank to the valve member and which operates at least until the system assumes the predetermined state.
That is, in this fuel tank system, the valve member remains closed and the cooling means is in operation until the system assumes the predetermined state. Then, if the system assumes the predetermined state, the valve member is opened and vapor is introduced into the canister. Thus, generation of vapor can efficiently be inhibited in accordance with the cooling capacity of the cooling means.
Further, by activating the cooling means, the amount of vapor introduced into the canister is reduced. Thus, it is possible to make the canister compact and reduce the amount of emission substances.
The cooling means may be provided either in the fuel tank or in the evaporation passage from the fuel tank to the valve member. In addition, it is also possible to provide the cooling means in both of them. In the case where the cooling means is provided in the fuel tank, it is possible to directly inhibit evaporation of fuel by cooling liquid fuel. In the case where the cooling means is provided in the evaporation passage from the fuel tank to the valve member, it is possible to reduce the amount of vapor introduced into the canister.
In the aforementioned aspect of the present invention, the predetermined state for opening the valve member may be a state of a high temperature which exceeds a predetermined temperature that has been set in advance.
Thus, the valve member remains closed and the cooling means is in operation until a the temperature exceeds the predetermined temperature that has been set in advance. In a state of a high temperature exceeding the predetermined temperature, the valve member is opened. This makes it possible to efficiently inhibit generation of vapor.
In the aforementioned aspect of the present invention, the predetermined state for opening the valve member may be a state of a high pressure which exceeds a predetermined pressure that has been set in advance.
Thus, the valve member remains closed and the cooling means is in operation until the pressure exceeds the predetermined pressure that has been set in advance. In a state of a high pressure exceeding the predetermined pressure, the valve member is opened. This makes it possible to efficiently inhibit generation of vapor.
In the aforementioned aspect of the present invention, refueling detection means for detecting a refueling state of the fuel tank may be provided, and the predetermined state may be a refueling state detected by the refueling detection means.
Thus, the valve member is closed in a state where the refueling detection means has not detected a refueling state (a state where no fuel is being refueled). If the refueling detection means has detected a refueling state, the valve member is opened and vapor is introduced into the canister. Also in this case, the amount of vapor introduced into the canister is reduced by activating the cooling means. Thus, it is possible to make the canister compact and reduce the amount of emission substances.
In the aforementioned aspect of the present invention, the valve member may include a control valve which is controlled by control means and a vent valve which is set to an open-valve pressure higher than a minimum open-valve pressure of the control valve.
Thus, regardless of the predetermined state (the high-temperature state, the high-pressure state or the refueling state), the control valve can be controlled by the control means and closed. While the control valve is thus closed, even if the pressure in the fuel tank has become higher than a minimum open-valve pressure of the control valve, the open-valve pressure of the vent valve is set higher than the minimum open-valve pressure of the control valve. Therefore, the vent valve remains closed until it reaches its own open-valve pressure. For example, even if the interior of the fuel tank has reached a high pressure in a parked state of the vehicle, it is possible to prevent vapor from being discharged from the fuel tank.
According to a second aspect of the present invention, there is provided a vapor gas inhibiting device for a fuel tank comprising a control valve which is disposed in a communication passage by which a fuel tank communicates with a canister, a control device which performs open-close control of the control valve in accordance with a state of a vehicle, and pressure detection means which detects an internal pressure of the fuel tank, wherein the control device controls the control valve such that a speed of change in internal pressure of the fuel tank becomes equal to or smaller than a predetermined value, based on an output value of the pressure detection means.
Thus, the control device controls the control valve such that the speed of change in internal pressure of the fuel tank becomes equal to or smaller than a predetermined value, based on an output value of pressure detection means for detecting an internal pressure of the fuel tank. As a result, the speed at which vapor is discharged from the interior of the fuel tank can be limited to a value that enables vapor to be adsorbed effectively in the canister. Thus, it is possible to improve the efficiency in adsorbing vapor.
According to a third aspect of the present invention, there is provided a vapor gas inhibiting device for a fuel tank comprising a control valve which is disposed in a communication passage by which a fuel tank communicates with a canister, a control device which performs open-close control of the control valve in accordance with a state of a vehicle, and flow rate detection means which detects a flow rate of vapor in the communication passage, wherein the control device controls the control valve such that a flow rate of vapor in the communication passage becomes equal to or smaller than a predetermined value, based on an output value of the flow rate detection means.
Thus, the control device controls the control valve such that the flow rate of vapor in the communication passage becomes equal to or smaller than a predetermined value, based on an output value of the flow rate detection means which detects a flow rate of vapor in the communication passage by which the fuel tank communicates with the canister. As a result, the speed at which vapor is discharged from the interior of the fuel tank can be limited to a value that enables vapor to be adsorbing effectively in the canister. Thus, it is possible to improve the efficiency in adsorbing vapor.
According to a fourth aspect of the present invention, there is provided a vapor gas inhibiting device for a fuel tank comprising a control valve which is disposed in a communication passage by which a fuel tank communicates with a canister, a control device which performs open-close control of the control valve in accordance with a state of a vehicle, and a temperature sensor which is disposed in the communication passage, wherein the control device controls the control valve based on a value detected by the temperature sensor.
Thus, the control device controls the control valve based on a value detected by the temperature sensor disposed in the communication passage by which the fuel tank communicates with the canister, whereby it becomes possible to ensure high efficiency in condensing and adsorbing vapor flowing through the communication passage in the canister.
In the aforementioned aspect of the present invention, cooling means may be provided in the communication passage, and the control device may be designed to control the control valve based on a value detected by the temperature sensor mounted to the cooling means such that sufficient cooling effect is obtained from the cooling means, and to restrict a flow rate of vapor to a predetermined value or less.
Thus, for example, immediately after the start of the cooling operation by means of the cooling means, the cooling means has not been cooled completely. Therefore, a sufficient cooling effect cannot be achieved. Thus, until the temperature detected by the temperature sensor becomes equal to or lower than a predetermined temperature, that is, until a sufficient cooling effect is achieved by the cooling means, the control device controls the control valve and restricts a vapor flow rate to a predetermined value or less so that predetermined cooling effect is achieved.
According to a fifth aspect of the present invention, there is provided a vapor gas inhibiting device for a fuel tank comprising a control valve which is disposed in a communication passage by which a fuel tank communicates with a canister, a control device which performs open-close control of the control valve in accordance with a state of a vehicle, pressure detection means which detects an internal pressure of the fuel tank, and storage means which stores a target internal pressure of the fuel tank, wherein the control device controls the control valve such that the interior of the fuel tank assumes the target internal pressure within a predetermined period, based on a difference between an internal pressure of the fuel tank upon the opening of the control valve and the target internal pressure.
Thus, the control device controls the control valve such that the interior of the fuel tank reaches a target internal pressure within a predetermined period, based on a difference between the internal pressure of the fuel tank upon the opening of the control valve and the target internal pressure stored in the storage means. As a result, it is possible to improve the efficiency in adsorbing vapor and bring the interior of the fuel tank to the target internal pressure within a predetermined period.
In the aforementioned aspect of the present invention, the predetermined period may be a period from operation of opening the lid to operation of opening the cap while refueling.
Thus, the internal pressure of the fuel tank can be shifted to the target internal pressure within the period from operation of opening the lid to operation of opening the cap while refueling. Therefore, it is possible to reduce the amount of vapor discharge out of the fuel filler neck.
According to a sixth aspect of the present invention, there is provided a vapor gas inhibiting device for a fuel tank comprising a control valve which is provided in a passage by which a fuel tank communicates with a vapor gas collecting device and which is opened during refueling operation, wherein the control valve is composed of a refueling valve and a pressure relief valve which are disposed in parallel and wherein the pressure relief valve is smaller in diameter than the refueling valve.
Thus, the large-diameter refueling valve and the pressure relief valve are selectively opened or closed, whereby it becomes possible to perform flow rate control in the control valve with ease.
In the aforementioned aspect of the present invention, the diameter of the refueling valve may be set such that a flow rate of vapor gas flowing through the refueling valve can be set to a flow rate enabling pressure relief of the fuel tank to be completed within a predetermined period.
Thus, the pressure relief of the fuel tank can be completed within the predetermined period by the opening of the refueling valve.
In the aforementioned aspect of the present invention, the diameter of the pressure release valve may be set such that a flow rate of vapor gas flowing through the pressure release valve is restricted to a flow rate enabling the vapor gas to be adsorbed in the vapor gas collecting device.
Thus, if the pressure relief valve has been opened, the diameter of the pressure relief valve restricts the flow rate of vapor gas passable through the pressure release valve to a flow rate enabling the vapor gas to be adsorbed in the vapor gas collecting device. As a result, the vapor collecting device can reliably adsorb hydrocarbon contained in vapor gas.
In the aforementioned aspect of the present invention, the refueling valve may be opened after the pressure relief valve has been opened.
Thus, if the internal pressure of the fuel tank in opening the control valve is high, vapor gas is caused to flow from the side of the fuel tank to the side of the vapor gas collecting device through the pressure release valve which is relatively small in diameter. Therefore, the vapor gas collecting device can reliably adsorb hydrocarbon contained in vapor gas. Further, after the pressure relief valve has been opened and the internal pressure of the fuel tank has dropped, the refueling valve, which is relatively large in diameter, is opened. Therefore, the opening force of the refueling valve can be reduced. After the pressure release valve has been opened, the refueling valve, which is relatively large in diameter, is opened so that vapor gas flows from the side of the fuel tank to the vapor gas collecting device. Therefore, the period required to relief a pressure in the fuel tank (the period required for vapor gas to flow from the side of the fuel tank to the side of the vapor gas collecting device) can be reduced.
In the aforementioned aspect of the present invention, the refueling valve may be closed in a running state of the vehicle.
Thus, by keeping the refueling valve closed in a running state of the vehicle, it becomes possible to inhibit a more than necessary amount of vapor gas from flowing from the side of the fuel tank to the side of the vapor gas collecting device.
According to a seventh aspect of the present invention, there is provided a vapor gas inhibiting device for a fuel tank comprising a control valve which is opened during refueling operation and which is provided in a passage by which a fuel tank communicates with a vapor gas collecting device, a communication device by which the fuel tank communicates with the vapor gas collecting device when driving an engine, and engine start means which starts the engine unless the control valve is opened during refueling operation.
Thus, if the control valve is not opened during refueling operation, and if the internal pressure of the fuel tank has not been lowered, the engine start means starts the engine. As a result, the fuel tank communicates with the vapor gas collecting device by the communication device. Therefore, even if the control valve is not opened during refueling operation, vapor fuel gas in the fuel tank can be fed to the vapor gas collecting device. Consequently, it becomes possible to lower the internal pressure of the fuel tank.
In the aforementioned aspect of the present invention, the control valve may be an solenoid valve, and the communication device may have a passage bypassing the solenoid valve and a diaphragm valve provided in the passage, and a negative pressure chamber of the diaphragm valve may communicate with a portion downstream of the solenoid valve.
Thus, if the solenoid valve is not opened during refueling operation, and if the internal pressure of the fuel tank has not been lowered, the engine start means starts the engine. As a result, the diaphragm valve can be opened by an intake negative pressure of the engine, so that the fuel tank comes into communication with the vapor gas collecting device. Thus, even if the solenoid valve is not opened during refueling operation, vapor fuel gas in the fuel tank can be fed to the vapor gas collecting device. Consequently, it becomes possible to lower the internal pressure of the fuel tank.
In the aforementioned aspect of the present invention, the engine start means may be designed to start the engine only if it is confirmed that the vehicle has been braked.
Thus, the engine is startn only if it is confirmed that the vehicle has been braked. Consequently, it becomes possible to improve safety.